Manipulating multiple images: slider values are applied incorrectly

[JFHoelscher]

When manipulating multiple images, different values of the same sign for a setting result in the same outcome.
For example: Enter {"export_format":"PNG", "Settings":{"Contrast":[-100, -50, 0, 50, 100]}} in imageIteratorSettings.json, open Lightroom, select multiple Images (I tested it with 10 images) and apply the Plugin. The resulting images for Contrast -50, 0 and 50 will look different; But the result for Contrast -50 will be the same (i.e. all pixel values are the same) as for -100, and the result for 50 the same as for 100. This problem does not occur if you select only one image.

[JFHoelscher]

Two images are in fact enough to reproduce the problem.